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I have a Linux server running SLES11 SP4 which uses open-iscsi and multipathing to connect to a LUN that is presented from an Open-E DSS v7 storage cluster with active/passive failover.

The Linux server db03 has its interface bond0 with the IP 10.0.100.66/22 in our iSCSI Network. Each side of the Open-E cluster has two IPs in the iSCSI network: 10.0.100.71 and 10.0.100.72 on the first node and 10.0.100.73 and 10.0.100.74 on the second.

So when no failover has occured, discovery looks like this:

db03:~ # iscsiadm -m discovery -t sendtargets -p 10.0.100.71:3260
10.0.100.71:3260,1 opene.lun602
10.0.100.72:3260,1 opene.lun602

With both targets connected this is the multipathing status:

db03:~ # multipath -ll
opene.lun602 (2697a42a45d5dcbdb) dm-0 SCST_BIO,izcegeu6eeb2jaeJ
size=500G features='0' hwhandler='0' wp=rw
`-+- policy='round-robin 0' prio=1 status=active
  |- 7:0:0:0 sda        8:0   active ready running
  `- 8:0:0:0 sdb        8:16  active ready running

In case of a failover both these connections go into failed faulty, I am left with 0 paths and all I/O errors until the kernel decides to remount the filesystem read-only.

At that point I can manually try another discovery, connect the two other targets, ... But no kind of failover happens automatically on the Linux side of things.

So I wonder:

  • Is there a way that linux can regularly rediscover for changes like these? I could not find any.

  • Is there a way to tell the Open-E DSS software to announce the other paths but signal that they are backup? (At one point in time we managed to have the cluster show all 4 paths, but they were incorrectly shown as active ready which clearly can't be a good idea together with an active/passive cluster where you are only ment to direct I/O to the active part.)

  • How is VMWare handling this? A VMWare Cluster connected to another LUN that is configured in the same manner shows no such problems.

For reference this is my multipath.conf:

cat /etc/multipath.conf
multipaths {
    multipath {
        wwid        2697a42a45d5dcbdb
        alias       opene.lun602
    }
}
devices {
    device {
        vendor          "SCST_FIO|SCST_BIO"
        product         "*"
        path_selector       "round-robin 0"
        path_grouping_policy    multibus
        rr_min_io       100
    }
}
1

I have a Linux server running SLES11 SP4 which uses open-iscsi and multipathing to connect to a LUN that is presented from an Open-E DSS v7 storage cluster with active/passive failover.

Ping Open-E unfortunately very close to being just missing support. These guys use fork-out from SCST target with some serious mods so everything people will recommend based on a "common" SCST knowledge may or may NOT work while people who had worked with Open-E before are rare for a very good reason. Sorry about that!

Multipath on ESXi is another story. To make your update work reliably you'll most probably end with a node restart. Perfect wrap up here:

http://www.codyhosterman.com/2015/03/esxi-iscsi-multipathing/

Good luck!

| improve this answer | |
  • 2
    +1 to @BaronSamedi1958, Open-E is outdated in general and have really crappy support. I would recommend any well-known industry standard vendor. VSAN for VMWare is a way better choice or any other solid SDS vendor you may like. Starwinds or HPE VSA are also very good and mature products perfectly supported as well. – Net Runner Apr 25 '16 at 4:59

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